The Development and Comparison of Two Polarimetric Calibration Techniques for Ground-Based Circularly Polarized Radar System

Abstract

Abstract-Two techniques are described for the calibration of ground-based (GB) circularly polarized (CP) full polarimetric radars. The techniques are based on the point target calibration approach that uses various types of canonical reflectors with different orientations. Specifically, the calibration methods for linearly polarized (LP) radar proposed by Wiesbeck et al. and Gau et al. are selected and adapted to CP with suitable reflectors. The applicability of the techniques is examined through C-band scatterometric and synthetic aperture radar (SAR) measurements in an anechoic chamber. For the scatterometric mode, comparisons of calibrated channel imbalances with theoretical values show agreement within ±0.3 dB in amplitude and ±5 • in phase. The crosstalk between the channels is also reduced by ∼ 5 to 30 dB after calibration. For the SAR mode, calibrated scattering matrix of a vertical wire target exhibits significant elimination of distortions between channel amplitudes and phases. The effect of calibration on target parameter retrieval is also investigated through the Cloud-Pottier eigenvector-based decomposition. Both calibration techniques are shown to yield improved accuracy of entropy-alpha (H-ᾱ) distributions and orientation angle (β) values.

Analysis of Dual- and Full-Circular Polarimetric SAR Modes for Rice Phenology Monitoring: An Experimental Investigation through Ground-Based Measurements

“…Here, we introduce the FLP calibration method proposed by Wiesbeck et al [25] as a suitable and an effective way for calibrating the ground-based LP-radar systems. To apply this method to CP-radar, an error model in circular polarization basis is constructed [26] [T] can be estimated, as explained in detail in our previous study [26]. Empty room calibration is also needed within the steps to extract the isolation distortion matrix [I], which can be performed easily by measuring a target free scene.…”

Ku Band Terrestrial Radar Observations by Means of Circular Polarized Antennas

“…Other papers have been published where polarimetry is used for the specific goals of characterizing advanced reflectors for calibration [18]. Circular polarization (CP) backscattering using a GB-SAR has been investigated in [19,20], and calibration of the used apparatus was carried out with a rigorous approach in a controlled environment, and with reference targets. In particular, in [19], the authors provide for the first time the results of a set of SAR laboratory experiments, where circular polarization acquisitions are discussed.…”